The objectives are to study several aspects of the structure and function of the aging nervous system. We will use organotypic cultures to study the effects of brain reactive serum antibody from old animals and elderly normal and demented people, and also to study the development and effect of experimentally induced lipofuscin. Using the Golgi technique, the dendritic arbor a) of human olivary neurons will be analyzed for the effect of lipofuscin; and b) of rabbit neurons for the effect of aluminum induced tangles. Axoplasmic flow will be examined in dystrophic axons of aged rats. The cerebral extracellular space of young and old rats will be quantified with chemical markers.